1. Field
The present invention relates to wireless communication, and more particularly, to an apparatus and method for transmitting information about power headroom in a multi-component carrier system.
2. Discussion of the Background
A wireless communication system uses one bandwidth for data transmission. For example, the 2nd generation wireless communication system uses a bandwidth of 200 KHz to 1.25 MHz, and the 3rd generation wireless communication system uses a bandwidth of 5 MHz to 10 MHz. In order to support an increasing transmission capacity, the bandwidth of the recent 3GPP LTE or 802.16m continues to be extended up to 20 MHz or higher. To increase the bandwidth may be considered to be essential so as to increase the transmission capacity, but to support a great bandwidth even when the level of required Quality of Service (QoS) is low may generate great power consumption.
In order to solve the problem, there has emerged a multi-component carrier system in which a component carrier having one bandwidth and the center frequency is defined and data is transmitted or received in a wide band through a plurality of component carriers. That is, a narrow band and a wide band are supported at the same time by using one or more component carriers. For example, if one component carrier corresponds to a bandwidth of 5 MHz, a maximum 20 MHz bandwidth can be supported by using four component carriers.
A method of a base station efficiently using the resources of a mobile station is to use power headroom information provided by the mobile station. The power headroom information is essential information for efficiently allocating uplink resources in wireless communication and reducing the battery consumption of a mobile station. When the mobile station provides the power headroom information to the base station, the base station can estimate maximum transmission power in uplink that the mobile station can withstand. Accordingly, the base station can perform uplink scheduling within the range of the estimated maximum transmission power in uplink.
Power headroom for each component carrier has a relatively small variance. Meanwhile, when a plurality of component carriers is dynamically scheduled, the variance may become relatively great. For this reason, the power headrooms of the component carriers must be taken into account individually or overall.